these popups are usually adverts. can you run a scan with malwarebytes please. It seems strange that you didn't get it on other browsers too. Please can you run a scan with malwarebytes. also can you provide a screenshot or photo of the message that you received so that I can confirm. Instructions for how to take screenshots can be found here --->
http://www.take-a-screenshot.orgLink & instructions for Malware Bytes -
1. Download the latest official version of Malwarebytes Anti-Malware Free:
https://www.malwarebytes.org/mwb-download/2. Once download is finished, double-click on mbam-setup.exe file to start the installation process and then follow the prompts to install this product.
3. On the "Scan" tab, select Threat scan and then click on the "Start Scan" button to start scanning your computer for any possible infections.
4. Malwarebytes’ Anti-Malware will start scanning your computer for any malicious files.
5. When the scan is finished a message box will appear, click OK to continue.
6. You will be presented with a screen showing you the malware infections that Malwarebytes Anti-Malware has found on your computer.
Make sure all the infected objects are Checked (Ticked) for removal and then click on the Remove Selected button to remove them.